Abstract

Supercurrent decay measurements of nano-superconducting quantum interference devices (SQUIDs) based on niobium constrictions (Dayem bridges) are reported. Such measurements provide useful information for applications that employ the SQUID as a trigger where the sensor works on the zero voltage state. The nanodevice consists of a niobium thin film (30 nm thick) ring with a hole side length of 200 nm including two Dayem bridges of . The measurements of the switching current distribution from the zero voltage state and the related escape rate, as function of the bias current, have been performed by a low noise fly time technique. The experimental data have shown an intrinsic current fluctuation less than 0.2% of the critical current at liquid helium temperature, corresponding to an intrinsic sensormagnetic flux resolution of a few . The theoretical predictions based on the thermal escape process theory in the moderately damping limit are in a reasonable agreement with the experimental data.

Received 04 November 2008Accepted 15 January 2009Published online 09 February 2009

Acknowledgments:

The authors are grateful to A. Bruno for the help given during the measurements. This work was partially supported by Italian MiUR under the project “Sviluppo di componentistica superconduttrice avanzata e sua applicazione a strumentazione biomedica” (Grant No. L 488/92, Cluster 14-Componentistica Avanzata).